On the other hand, I cannot imagine a situation where I set the aperture AFTER focusing, so I don't see a big issue here.

Unless you're shooting wide open or focusing manually with the DoF Preview button pressed, you're stopping down after focusing every time you shoot. AF is always performed with the lens wide open, regardless of the aperture selected. The lens stops down just before the shot, and that's when focus shift occurs.

Do you see a bigger issue now?

Ah, thanks for the edification. Indeed, then it would be a VERY BIG ISSUE, and then I wonder why that hasn't been all over the internet already! Maybe sample variation did play a role here? BTW, not that I am personally interested in this lens, but would this be true even if one is back-button focusing?

I was waiting for the reviews to come in , and i would have considered it IF it was a stellar performer: sharp everywhere, great contrast, resistant to flare, low distortion etc etc. But it has very little to offer over my 24-105 and it's only 70g lighter, ... so it's dead to me.

On the other hand, I cannot imagine a situation where I set the aperture AFTER focusing, so I don't see a big issue here.

Unless you're shooting wide open or focusing manually with the DoF Preview button pressed, you're stopping down after focusing every time you shoot. AF is always performed with the lens wide open, regardless of the aperture selected. The lens stops down just before the shot, and that's when focus shift occurs.

Do you see a bigger issue now?

If you manual focus in Live View, then the focus shift is irrelevant.

It's a deal breaker for me. I have zero interest in a lens with focus shift problems.

Here are some reviews and hands-on previews, all of which fail to mention any sort of fous shift issue with the lens. Is everyone else's testing methods so non-rigorous that they miss this problem, is it in fact not a problem during real life use of the lens, or did photozone get a bad lens?

I'll just link the F/4 data -- see attachments. It's pretty clear that the new F/4 IS lens is very good, but I believe the world will disregard it for petty reasons (i.e. this lens isn't new compared to the 24-105) and legitimate value-based reasons (i.e. overpriced).

Again, I'm not supporting this lens as offered -- it's clearly overpriced. But to bash it just on three specs (range/speed/IS) is a little nearsighted, IMHO. This lens will be used, it will be loved, and it will build a following just like the 24-105, though perhaps for different reasons.

While I trust their methods and unbiasedness at Photozone, as several have pointed out, the sheer number of lenses not tested is also an important aspect to consider when reading the different reviews.

How many lenses does TDP, DPReview, DXO use for tetsing lenses?

For me personally I like my 24-105 and my copy delivers sharp pictures and is a great lens (apart from a sliding movement of the inner barrel when carrying it around (easily fixed by strapping on a plastic/rubber ring that girls wear around their arms, bought in accesorize)). I also believe that the F4 vs. F2.8 is somewhat less of a showstopper now that the latest cameras have had great improvements in ISO, which also speaks for the new 24-70 IS. To me, the incrimental improvement in sharpness vs. the one I know and like is too small to justify such an investment. If the 24-70 II were to drop in price.....

I'll just link the F/4 data -- see attachments. It's pretty clear that the new F/4 IS lens is very good, but I believe the world will disregard it for petty reasons (i.e. this lens isn't new compared to the 24-105) and legitimate value-based reasons (i.e. overpriced).

Again, I'm not supporting this lens as offered -- it's clearly overpriced. But to bash it just on three specs (range/speed/IS) is a little nearsighted, IMHO. This lens will be used, it will be loved, and it will build a following just like the 24-105, though perhaps for different reasons.

If you want to correct the 24-105's distortion, you'll end up with resolution far less than that of the new 24-70/4 IS. That by itself shows that this is a much better lens all around than the aging 24-105, and you can also focus much more closely.

If you want to correct the 24-105's distortion, you'll end up with resolution far less than that of the new 24-70/4 IS. That by itself shows that this is a much better lens all around than the aging 24-105, and you can also focus much more closely.

I did mention it. This one has the lowest distortion of them all. MUCH less than the tamron at 24mm, much less than 24-105 at 24mm, less than the 24-70 II at 24mm, only the 24mm primes do better for distortion at 24mm.

On the other hand, I cannot imagine a situation where I set the aperture AFTER focusing, so I don't see a big issue here.

Unless you're shooting wide open or focusing manually with the DoF Preview button pressed, you're stopping down after focusing every time you shoot. AF is always performed with the lens wide open, regardless of the aperture selected. The lens stops down just before the shot, and that's when focus shift occurs.

Do you see a bigger issue now?

Ah, thanks for the edification. Indeed, then it would be a VERY BIG ISSUE, and then I wonder why that hasn't been all over the internet already! Maybe sample variation did play a role here? BTW, not that I am personally interested in this lens, but would this be true even if one is back-button focusing?

On the other hand, I cannot imagine a situation where I set the aperture AFTER focusing, so I don't see a big issue here.

Unless you're shooting wide open or focusing manually with the DoF Preview button pressed, you're stopping down after focusing every time you shoot. AF is always performed with the lens wide open, regardless of the aperture selected. The lens stops down just before the shot, and that's when focus shift occurs.

Do you see a bigger issue now?

Ah, thanks for the edification. Indeed, then it would be a VERY BIG ISSUE, and then I wonder why that hasn't been all over the internet already! Maybe sample variation did play a role here? BTW, not that I am personally interested in this lens, but would this be true even if one is back-button focusing?

Yes, true no matter how you autofocus.

Maybe they are dealing with it in the lens AF firmware? Basically an "on the fly AFMA based on aperture" of sorts perhaps? Would be interesting to compare the observed shift doing manual chart shot vs AF chart shot at various apertures.

If you want to correct the 24-105's distortion, you'll end up with resolution far less than that of the new 24-70/4 IS. That by itself shows that this is a much better lens all around than the aging 24-105, and you can also focus much more closely.

But at least the distortion of the 24-105L is correctable. Out-of-focus shots caused by the focus shifting of the 24-70 f4L is not.

BTW, I wouldn't consider the focus shift an automatic deal breaker for me, since I don't use macro that often and typically shoot close to wide open. But it is another small reason why I'm not expecting to "upgrade" from the 24-105L, with price / loss of 35mm on the long end the main reasons. The 24-105L is a great walkaround lens, the 24-70 not as much (to me at least).

Besides the RSA in macro mode at 70 mm, what else is work this lens? Nothing. I seldom use macro mode on many of my lenses, so this is a none issue for me.

I would like to have seen a comparison between the 24-70 F2.8II, 24-105 and this lens for IQ in non-macro situations.

I agree, if the focus shift is only in macro mode, then it's a non-issue. Macro shots mean manual focus, usually with live view. There will be no focus shift in live view with manual focus because the aperture will be at your selected setting while you focus.

While I trust their methods and unbiasedness at Photozone, as several have pointed out, the sheer number of lenses not tested is also an important aspect to consider when reading the different reviews.

How many lenses does TDP, DPReview, DXO use for tetsing lenses?

You make a fair point. From the reviews I've read, it appears that each site has strengths and weaknesses:

Roger at LR is king of sharpness data from my perspective, b/c he tests all of LRs stock of the same lens (in some cases, dozens of the same lens). That trumps most everyone out there for data, but he's not the thoughtful tips/feedback/insights guy that Bryan Carnathan is. Roger also has (IMHO) massive street cred on being a camera nerd first and a fanboy last. He'll blow any design out of the water if it underperforms.

TDP -- Carnathan does test multiple copies but not a huge number. He brings up copy to copy variation when something odd occurs and obtains new glass to verify odd findings. See his Tamron 24-70 IS and new Mk II 24-70 reviews -- fishy stuff came up and he itemized the differences.

Further, his site is more of a broad read of useability and his personal (though admittedly expert) take on things. His site excels at fun image-level comparisons of all the lenses taking the same shot (or test page) from a tripod, and then allowing you to mouseover to see what's going on: L vs. non-L vs. Sigma, aperture, ISO, etc.

I read his site fairly religiously for all-around reasons. It's thoughtful, useful commentary from a knowledgable user. But his is a world of insight and adjectives -- it's not a lab-like mountain of details.

Photozone has the most nicely broken down sharpness data that I can read easily. They have middle/border/extreme resolution data for many focal lengths on a zoom, and they report it for most common apertures selected. Very helpful. This is a site opens your mind a bit as you tend to comparison shop. At a site like this, you see non-L glass punching its weight brilliantly against L glass if you stop it down just a shade. Big limitation? I believe it's only one lens they test.

DXOs interesting angle is having combinatorial data of bodies + lenses. No idea how many lenses they actually test. I don't read this site much as DXO has (groan) their own metrics on their own hardware that I haven't bothered to learn how to read. I still don't understand their data fully.

I don't read DPreview reviews as they require a dozen page turns to get ad views. Fail. They are wasting my time versus their competitors.

I don't read Ken Rockwell much, but my goodness, if you want a fine detail about metal vs. plastic, if the front element rotates during focusing, how many points on the sunstar created when stopping down, etc. then he's your guy. Absurd little details for the nerdy camera lover. TDP has some of this, too, but it's inconsistently reported from review to review.

For me, I trust:

TDP for everything but data -- it's just there, easy to find, and thoughtfully explained.

Roger at LR for hard sharpness numbers. End of story.

Photozone for quick, easy comparison of two lenses I might be considering